We plan to analyze relationships between the structure of neurons and glia in the amphibian and turtle retina and their function. The structure of single cells will be determined by intracellular staining with horseradish peroxidase or lucifer yellow or by a new retrograde HRP staining method that has been worked out in the laboratory. A computer-microscope system in CORE will be used to enter the anatomical data and provide plots of the cell in flatmount and cross-sectional views. The function of neurons and glia will be studied on three levels. 1) Single ganglion and amacrine cells of the intact retina will be studied with biophysical measurements obtained with whole cell recording applied to the intact, photactive retina. These measurements will be correlated with structure to determine the electrotonic length of dendritic trees and their functional properties, including a determination of the membrane resistance necessary to match the input resistance. 2) Enzymatically dissociated Muller cells will be studied to analyze how asymmetric distributions of ionic channels alters the shape of the charging curve. Compartmental models of single Muller cells and systems of them will be used to test hypotheses concerning differences between the electrical charactristics of these cells as measured in vivo vs. in vitro. 3) We will analyze the horizontal cell network in the turtle retina by combining physiological studies with computer analysis and simulations. We propose to test our recent hypothesis that synaptic spines of the horizontal cells play a role in determining the spatial summation properties of the horizontal cell network. Studies of single horizontal cells will be used to determine constraints of an electrical model.